[JJ_SO]

My my Scythels, what can I say if I see such a wall of words and knowledge?  B) I hope you don't expect me to understand/comprehend every bit of what you wrote nor could calculate some of those formulas. I don't want to defend LenScore, I just appreciate them as "another source" of collected data. If their process is actually that weak and full of flaws like it appears to be in your reply, how come they are more or less confirming your conclusion about those three lenses? Might be a coincidence...

 

I agree most of your conclusions about those lenses. However, I ended up with the Sigma because of 

• good experiences with two other Art-lenses (now three)
  
• at the time there was no Tamron available
  
• I get 24-105 instead of 24-70 at a smaller price about the same weight (more or less)
  
• the Sigma USB-dock does a nice job, though time-consuming and would be easier if I could wire the lens directly to a PC
  
• I already have fast primes, my zoom doesn't need to be super fast (and those are very tricky to correct and still weaker wide open)
  
• in Switzerland, the Sigma importer gives a free once a-year-service-check (without materials). Lifelong…
  
• Tamron's service is based in Germany, it's complicate, expensive (transport costs are huge) and takes a lot time to let them check a lens, but that's only my special situation. However, I'd include the service situation (and the experiences with) in my decision.
  

I don't want to talk your doubts about mechanical design away. I'm just more confident since none of the 4 Sigmas (Art series) and none of the other 4 I had with Pentax showed mechanical flaws or was a repair case. While the pretty expensive Nikkor 85/1.4G needed a new focus drive after only two years, no rain or other weather conditions involved. Of course, there's no Sigma 85/1.4 Art to compare for me. Yet. But here comes the next list where Sigma does a little bit better than Nikon

• both caps are better designed and don't slip out of my fingers
  
• the lens hood (okay, that's nothing for a zoom, because there it's useless in tele position) of the 50/1.4 Art makes the lens less sensitive to certain front light situations than even Zeiss' Otus round shaped hood is.
  
• they are better damped when manual focussing than the Nikons and there's no gap in the focus rings 
  

My conclusion is, Sigma cares a lot about details. Question is "also inside the lens?" Can't say, haven't open one yet.

 

Thanks a lot for your text about Interferometry. Like you said, a time consuming process and maybe not the best suitable for testing photographic lenses. I suspect, the interferometry test of those three lenses wouldn't come to surprisingly different results as the less precise/reliable MTF 50 test.

 

And right, DxO mark doesn't test all body-lens combinations. But they do more than anyone else out there and it's a good chance to find popular contemporary combinations tested - while PZ for each system (APS-C, FF, manufacturer) only tests on one body.

 

A last bit about your simulation of how Canon and Nikon tests could be interpolated by MP count: Canon uses AA filter, Nikon D750 doesn't - that IS increasing the resolution, but less than 10% (D800 / D800E being the only camera types to be comparable in this aspect)